Putting these facts together, it is a reasonable inference, and supported by the whole tenor of the history, that the Roman sea power controlled the sea north of a line drawn from Tarragona in Spain to Lilybæum (the modern Marsala), at the west end of Sicily, thence round by the north side of the island through the straits of Messina down to Syracuse, and from there to Brindisi in the Adriatic. This control lasted, unshaken, throughout the war. It did not exclude maritime raids, large or small, such as have been spoken of; but it did forbid the sustained and secure communications of which Hannibal was in deadly need.
On the other hand, it seems equally plain that for the first ten years of the war the Roman fleet was not strong enough for sustained operations in the sea between Sicily and Carthage, nor indeed much to the south of the line indicated. When Hannibal started, he assigned such ships as he had to maintaining the communications between Spain and Africa, which the Romans did not then attempt to disturb.
The Roman sea power, therefore, threw Macedonia wholly out of the war. It did not keep Carthage from maintaining a useful and most harassing diversion in Sicily; but it did prevent her sending troops, when they would have been most useful, to her great general in Italy. How was it as to Spain?
Spain was the region upon which the father of Hannibal and Hannibal himself had based their intended invasion of Italy. For eighteen years before this began they had occupied the country, extending and consolidating their power, both political and military, with rare sagacity. They had raised, and trained in local wars, a large and now veteran army. Upon his own departure, Hannibal intrusted the government to his younger brother, Hasdrubal, who preserved toward him to the end a loyalty and devotion which he had no reason to hope from the faction-cursed mother-city in Africa.
At the time of his starting, the Carthaginian power in Spain was secured from Cadiz to the river Ebro. The region between this river and the Pyrenees was inhabited by tribes friendly to the Romans, but unable, in the absence of the latter, to oppose a successful resistance to Hannibal. He put them down, leaving eleven thousand soldiers under Hanno to keep military possession of the country, lest the Romans should establish themselves there, and thus disturb his communications with his base.
Cnæus Scipio, however, arrived on the spot by sea the same year with twenty thousand men, defeated Hanno, and occupied both the coast and interior north of the Ebro. The Romans thus held ground by which they entirely closed the road between Hannibal and reinforcements from Hasdrubal, and whence they could attack the Carthaginian power in Spain; while their own communications with Italy, being by water, were secured by their naval supremacy. They made a naval base at Tarragona, confronting that of Hasdrubal at Cartagena, and then invaded the Carthaginian dominions. The war in Spain went on under the elder Scipios, seemingly a side issue, with varying fortune for seven years; at the end of which time Hasdrubal inflicted upon them a crushing defeat, the two brothers were killed, and the Carthaginians nearly succeeded in breaking through to the Pyrenees with reinforcements for Hannibal. The attempt, however, was checked for the moment; and before it could be renewed, the fall of Capua released twelve thousand veteran Romans, who were sent to Spain under Claudius Nero, a man of exceptional ability, to whom was due later the most decisive military movement made by any Roman general during the Second Punic War. This seasonable reinforcement, which again assured the shaken grip on Hasdrubal's line of march, came by sea,—a way which, though most rapid and easy, was closed to the Carthaginians by the Roman navy.
Two years later the younger Publius Scipio, celebrated afterward as Africanus, received the command in Spain, and captured Cartagena by a combined military and naval attack; after which he took the most extraordinary step of breaking up his fleet and transferring the seamen to the army. Not contented to act merely as the "containing"6 force against Hasdrubal by closing the passes of the Pyrenees, Scipio pushed forward into southern Spain, and fought a severe but indecisive battle on the Guadalquivir; after which Hasdrubal slipped away from him, hurried north, crossed the Pyrenees at their extreme west, and pressed on to Italy, where Hannibal's position was daily growing weaker, the natural waste of his army not being replaced.
The war had lasted ten years, when Hasdrubal, having met little loss on the way, entered Italy at the north. The troops he brought, could they be safely united with those under the command of the unrivalled Hannibal, might give a decisive turn to the war, for Rome herself was nearly exhausted; the iron links which bound her own colonies and the allied States to her were strained to the utmost, and some had already snapped. But the military position of the two brothers was also perilous in the extreme. One being at the river Metaurus, the other in Apulia, two hundred miles apart, each was confronted by a superior enemy, and both these Roman armies were between their separated opponents. This false situation, as well as the long delay of Hasdrubal's coming, was due to the Roman control of the sea, which throughout the war limited the mutual support of the Carthaginian brothers to the route through Gaul. At the very time that Hasdrubal was making his long and dangerous circuit by land, Scipio had sent eleven thousand men from Spain by sea to reinforce the army opposed to him. The upshot was that messengers from Hasdrubal to Hannibal, having to pass over so wide a belt of hostile country, fell into the hands of Claudius Nero, commanding the southern Roman army, who thus learned the route which Hasdrubal intended to take. Nero correctly appreciated the situation, and, escaping the vigilance of Hannibal, made a rapid march with eight thousand of his best troops to join the forces in the north. The junction being effected, the two consuls fell upon Hasdrubal in overwhelming numbers and destroyed his army; the Carthaginian leader himself falling in the battle. Hannibal's first news of the disaster was by the head of his brother being thrown into his camp. He is said to have exclaimed that Rome would now be mistress of the world; and the battle of Metaurus is generally accepted as decisive of the struggle between the two States.
The military situation which finally resulted in the battle of the Metaurus and the triumph of Rome may be summed up as follows: To overthrow Rome it was necessary to attack her in Italy at the heart of her power, and shatter the strongly linked confederacy of which she was the head. This was the objective. To reach it, the Carthaginians needed a solid base of operations and a secure line of communications. The former was established in Spain by the genius of the great Barca family; the latter was never achieved. There were two lines possible,—the one direct by sea, the other circuitous through Gaul. The first was blocked by the Roman sea power, the second imperilled and finally intercepted through the occupation of northern Spain by the Roman army. This occupation was made possible through the control of the sea, which the Carthaginians never endangered. With respect to Hannibal and his base, therefore, Rome occupied two central positions, Rome itself and northern Spain, joined by an easy interior line of communications, the sea; by which mutual support was continually given.
Had the Mediterranean been a level desert of land, in which the Romans held strong mountain ranges in Corsica and Sardinia, fortified posts at Tarragona, Lilybæum, and Messina, the Italian coast-line nearly to Genoa, and allied fortresses in Marseilles and other points; had they also possessed an armed force capable by its character of traversing that desert at will, but in which their opponents were very inferior and therefore compelled to a great circuit in order to concentrate their troops, the military situation would have been at once recognized, and no words would have been too strong to express the value and effect of that peculiar force. It would have been perceived, also, that the enemy's force of the same kind might, however inferior in strength, make an inroad, or raid, upon the territory thus held, might burn a village or waste a few miles of borderland, might even cut off a convoy at times, without, in a military sense, endangering the communications. Such predatory operations have been carried on in all ages by the weaker maritime belligerent, but they by no means warrant the inference, irreconcilable with the known facts, "that neither Rome nor Carthage could be said to have undisputed mastery of the sea," because "Roman fleets sometimes visited the coasts of Africa, and Carthaginian fleets in the same way appeared off the coast of Italy." In the case under consideration, the navy played the part of such a force upon the supposed desert; but as it acts